Apparatus for telephone-lines.



No. 758,703. PATENTED MAY 3, 1904 G. E. SGRIBNER & J. L. MGQUARRIE.

APPARATUS FOR TELEPHONE LINES. APPLICATION FILED APE. 2. 1900.

N0 MODEL.

UNITED STATES CHARLES E. SCRIBNER AND JAMES L.

Patented May 3, 1904.

PATENT OFFICE.

MCQUARRIE, OF CHICAGO,

ILLINOIS, ASSIGNORS TO THE WVESTERN ELECTRIC COMPANY, OF

CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

SPECIFICATION forming part of Letters Patent No. 758,703, dated May 3, 1904.

Application filed April 2, 1900.

To rt/I w/wm, it may concern.-

Be it known that we, CHARLES E. SCRIB- NER and J AMES L. MOQUARRIE, citizens of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Apparatus for Telephone-Lines, (Case No. 487 9,) of which the following is a full, clear, concise, and exact'description.

Our-invention concerns the construction and operation of so-called extension telephonelinesthat is to say, of lines extending from a central oflice to two or more substations; and its special features look to the supply of current from a source at the central office for exciting the transmitting-telephones at both substations. and the operation of signals between the substations and between each of the substations and the central oilice in conformity with the usual practice in the centralenergy exchange systems.

Our invention consists in general in arrangements of circuits by which either substation may call the other or may call the central oilice, by which either substation may speak with the other or with the central office, interference with conversation between the substations or between one of the stations and the central ofiice, being guarded against by suitable changes of the circuits, means for operating a signal atthe central otfice by switches or keys at the substations through the agency of current supplied from the central ofliee, and means for supplying and controllingcurrent for exciting the substation-telephone independently of the signal at the central ofiice.

Our invention is illustrated diagrammatically in the attached drawing.

This drawing represents a single extensionline connected with the usual and well-known signaling and current-supplying apparatus of the common batteryswitchboard, the substations being equipped with our improved apparatus for permitting inter-communication.

The line conductors 1 and 2 lead from the two substations A and B to the central oflice C, where they are normally connected with the poles of the central source (Z of energy. One

Serial No. 11,057. (No m0del.)

of the poles of this central source of current, that which is connected with the line cone ductors l, is connected to earth or to other suitable common return for the telephonelines. The line conductor 1 of the main line traverses the magnet-winding of a line-signal 0. Connection of both line conductors with the central source of energy is controlled by the switch-contacts of a cut-off relay f. The line is connected with the spring-jack g, which contains besides the terminal contacts of the line a local contact-ring, which forms the terminal of a portion 3 of a local circuit of battery (Z, which includes the magnet of the cutoff relay.

Plugs it and h are furnished for uniting lines, the line-contacts of the plugs being united in pairs through conductors leading to a central source of current, which may be the general source, (Z, through windings of a repeating-coil. This arrangement permits current to flow to united lines for exciting the substation-transmitters and working the signals and maintains the separation of the lines with respect to such flow of current, while forming the medium of connection between them for telephonic currents. Local contact-pieces ofthe plugs form the terminals of wires 4 and 5, which include supervisory signals and 11', associated with the plugs 7L and h. flhese local conductors are connected also with the battery (Z and serve to form closed local circuits through the magnets of the cut-off relays of lines with which the plugs are connected. In the line conductors 7 and 8 of the plug-circuit are located supervisory relays Z; and b, one in the path of current to each of the plugs, which relays control corresponding signals 11 and t" by means of shunts of the signals closed by the relays.

WVhile two batteries (marked (Z) are shown in the drawing, it is understood that in accordance with the usual practice a single central battery may be employed connected as indicated.

All the apparatus thus far described is that which is usual in common battery-switchboards.

In our invention we provide at the interinediate substation A a key Z. This key has two sets of switch-springs Z Z and Z and Z, respectively. The springs Z Z are provided with normal resting contact-anvils which are connected with the limbs 1 2 of the telephoneline, respectively, the limb Z being further controlled by the spring Z and its normal resting contact. The spring Z is provided with an outer contact against which it is ad apted to be pressed. A conductor 13 extends from the spring Z to ground, said conductor including an impedance-coil m This conduetor is controlled by the spring Z and its back-contact and is closed when the springs Z Z are wedged apart. The springs Z Z" are also adapted to be wedged apart, and so lifted from their resting contact-zinvils. Any suitable means may be adopted for operating these switch-springs; but we prefer to use the key of the general type described in Patent No. 564,457, dated July 21, 1896, to C. E. Scribner and F. R. McBerty, in which a doublefaced wedge of insulating material carried on one end of a pivoted lever oscillates between the presented ends of a pair of switch-springs to force the springs of either pair apart. Normally the pairs of springs are in the position shown; but either pair may be forced apart alternatively, as desired.

Each of the substations is furnished with the usual polarized call-bell m, receiving-telephone m, transmitting-telephone m induction-coil m and telephone-switch 172*. At station A the bell m is connected in a bridge 10 between line conductors 1 and 2, the bridge of the line being formed between the key and the central oflice. A condenser m is interposed in the bridge. The telephones m m are connected in a bridge 11 of the line-circuit controlled by the telephone switch m, this bridge being formed across the line conductors between the resting-anvils of switchsprings Z Z*.

The break in the line-circuit at the station A, controlled by the switch-spring Z of the key Z, is permanently shunted by a conductor 12, which is, however, rendered practically opaque to telephone-currents by animpedance-coil'm, contained in said conductor. We choose to combine the functions of this impedance-coil with those of a bell-magnet, the magnet-windings of the bell m being sufficient for our purpose. The bell should be of the single-stroke variety. These windings should be of comparatively low resistance, but of very high inductance. Another path 13 is formed between the stations A and B from line conductor 1 to earth or other common return, which also includes an impedancecoil m The continuity of this earth branch is controlled by the switch-contact Z A calling-key n, consisting of a lever and normal and alternate contacts, has its normal contacts interposed serially in the line conductor 1. Its alternate contact, against which the lever" is thrust in depressing the key, is connected with line conductor 2, so that the key when operated closes a bridge of the portion of the line-circuit leading to station E while breaking the line conductor near the station A. 1 A condenser s is interposed in line conductor 2 between the switch-springZ' and the point of connection of the shunt 12.

The apparatus at station B likewise comprises telephones, induction-coil, and telephone-switch, connected with the line conductors 1 and 2 in the same way as at station A. A call-bell 0, like the bell m at station A, is also furnished at station B, connected in a permanent ground branch from the line conductor 1. Calling-key 19 serves to close a ground branch 14 from line conductor 2 for calling the intermediate station A. If desired, a polarized bell m may beconnected in a bridge of the line-circuit at station B.

The above-described arrangement of apparatus and circuits provides that either of the substations may call and speak with the central office or may be connected at the central office with a corresponding line, that the central oflice may call and communicate with either substation, that either substation may call and talk with the other substation, the

energy for operating all the apparatus involved being derived from the central source (Z at the central station. The circuits taking part in these various usages of the apparatus may be traced in particular.

. A user of the telephone at station A may call the central oflice to initiate a connection by placing the key Z in position to cut the branches of the line conductor leading to station Bthat is, with the insulating-wedge between the springs Z Z*and taking the receiving-telephone m from its switch-hook. The movement of the lever of the telephone-switch closes bridge 11 of the line-circuit, and thus permits current to flow from battery (Z through line conductor 2, bridge 11, returning by line conductor 1 to battery (Z, which excites the line-signal The call-signal so displayed is answered by the operator in the usual way by inserting an answering-plug it in the springjack of the line, and after the attendant has learned the order from the calling-station connection may be established with the line wanted by means of plug it. Making connection with the calling-line by means of plug it breaks the normal connection of the line with the battery (Z, the break being effected by the cut-ofi relay f; but a new circuit of V the line to the same battery is formed through the plug-circuit 6 and 7, the new circuit including the supervisory relay and being thus adapted to control the supervisory signal 6 in correspondence with the position of the telephone-switch mf.

When the telephone at station A is not in use, the switch Z should be left in position to complete the line-circuit through to station B. \Vith the apparatus at the intermediate station A in such position the user of the telephone at station B, desiring to initiate a call, may accomplish it in the same way and may procure a connection with a different line in the central ofIice through the same system of circuits as those traced in the case of a call from the station A.

The operator at the central office may call either station A or B by inserting a plug lb into the spring-jack of the line and applying calling-current from a suitable generator (not shown in the drawing) to the metallic line-circuit. The calling-current will find circuit through bells m at each of the stations, and the user of the telephone at the desired station may be brought to the instrument by giving a preconcerted signal.

A user of the telephone at station A may send a call to the station E by depressing the key n at station A. The movement of this key permits a current to flow from battery (Z through line conductor 2 to station A, thence through the bell m and key a to line conductor 1, and therefrom to earth through the bell 0 at station B. It will be observed that the movement of the key also breaks the portion of the line conductor 1 returning to the central oflice, and thereby prevents'the operation of the line-signal during the transmission of this local call-signal. The user of the telephone at station B may under the same condition of the line call to the station A by depressing the key at station B. The movement of this key forms a circuit of battery (Z through line conductor 2, shunt-wire 12 at station A, and ground branch 14 at station B, which causes bell m. at station A to ring. In response to this call the telephone user at station A will place the switch Z in position to sever the line toward the central office-that is, will thrust the insulating-wedge between springs Z Z of the wedge. Spring Z is thus separated from its normal contact, and spring completes at its alternate contact the conductor 13, leading through impedance-coil m to earth. Current now flows from the central battery (Z out over conductor 2, through the telephone apparatus at station A to contact I, and thence to earth through the impedance-coil m Current also flows through conductor 12 at substation A to the extension of conductor 2, which leads to station B, and thence through the telephone apparatus at station B to earth, part flowing through the impedance-coil 0 direct to earth at station B and part returning by conductor 1 to station A, and passing thence through conductor 13 and coil 12: to earth. Both transmitters being thus supplied with current, the varying telephone-currents generated thereby are propagated over the metallic circuit 12 between the stations, passing through the condenser s, which is interposed in conductor is independent of the talking-circuits to the central oflice, and hence may be free from interference during conversation.

\Ve claim as new and desire to secure by Letters Patent 1. The combination with a telephone-line and a ground-return therefor, a battery connected between the ground-return and one line conductor, and a visible signal connected between the ground-return and the other line conductor, of a telephone at the substation in a bridge of the line-circuit, and a switch adapted to break the line conductor containing the signal and to connect the corresponding terminal of the telephone with the groundreturn; whereby battery may be supplied for exciting the transmittingtelephone independently of the signal when required.

2. In combination with a telephone-line from a central station to two substations, said line having two line conductors and an earthreturn, a source of current applied to one ofthe line conductors between the said conductor and the earth-return, and a visible signal in the other line conductor between the line and the earth-return, a transmitting and a receiving telephone at each of the substations in a bridge of the line-circuit, and a switch in the line conductor containing the signal between the central ofiiee and the first substation adapted to break the said line conductor and connect the part thereof leading to the distant substation with the ground-return; whereby the two substations may be supplied with current independently of the line-signal, as described.

3. The combination with a telephone-line and an earth-return therefor, a source of current applied to one of the line conductors between the said line and the earth-return, and a linesignal in the other line conductor between the line and the earth-return, a call-bell in a ground branch from the line conductor containing the signal at a substation, and a calling-key adapted to unite the line conductors directly while breaking the conductor containing the signal between the said point of junction and the signal, as described.

4:. The combination in an extension-line system leading from a central station to two substations, a source of current connected with the line-circuit at the central oflice, receiving and transmitting telephones in bridges of the line-circuits at the substations, said transmitting-telephones being adapted for operation by current derived from the line, a switch in the line adapted to sever the normal continuity of the line, and a by-path of high inductance and low resistance about said switch; whereby the transmitters may be supplied with current while the diversion of telephonic currents to the central oflice is prevented, as described.

5; The combination with a telephone-line extending from a central station to two substations and a return-circuit therefor, of a source of current connected between one line conductor and the return-circuit, and a visi ble signal connected between the other line between the telephone-bridge at the same station and the central office, a permanentlyclosed shunt of high impedance about said switch-contacts in the conductor with which the source of current is directly connected,

and a branch of high impedance between the other line conductor and the return-circuit closed bysaid switch in the same position, said switch when in its other position severing theline conductors between the substations, as described.

In witness whereof we hereunto subscribe our names this 9th day of February, A. D. 1900. I 7

CHARLES E. SCRIBNER. JAMES L. MGQUARRIE.

Witnesses:

ELLA EDLEY, DUNCAN E. WILLETT. 

